Move converted photon builders to standard particles

Converted photons have existed in the RD modules for a long time. More recently they were needed in B2CC and now also B2OC. It was discussed in the RTA WP3 meeting 14/10 that they should consequently be moved to standard_particles to avoid code duplication and ConfigurationError (previously seen before when including in B2CC modules and resolved under time pressure with a hack)

This MR moves the builders to standard_particles without changing any selections. Checked for no change in rates on RD and B2CC turbo/full/spruce lines.

This is required for !5401 (closed) in B2OC targeting EoY resprucing.